A tensile testing system and method for cast CPE films

Abstract

The application discloses a kind of tensile test system and method of casting CPE film, and test method includes steps S1-S9, the tensile test method of casting CPE film is used Test system includes: film material testing machine, area light source, camera and data processing system.The application is by tensile test to casting CPE film, the performance after the tensile of casting CPE film is comprehensively analyzed, further evaluates the grade of casting CPE film, avoids the influence of artificial subjective factor, can objectively, accurately evaluate the performance after the tensile of film, and directly obtains grade evaluation structure, effectively improves the efficiency of the quality detection of casting CPE film produced, and degree of automation is high.

Description

Technical Field

[0001] This invention relates to the field of performance testing technology for cast CPE films, and specifically to a tensile testing system and method for cast CPE films. Background Technology

[0002] Cast film is a non-stretched, non-oriented flat extrusion film produced by rapidly cooling melt casting. There are two methods: single-layer casting and multi-layer co-extrusion casting. Compared to blown film, its advantages include faster production speed, higher output, and significantly better film transparency, gloss, and thickness uniformity.

[0003] With continuous economic development and social progress, people are provided with a wide variety of consumer goods for their production and daily life. As we all know, packaging is indispensable for the packaging of various granules, electronic products, silicone, ear caps, and other materials. Cast CPE film is a commonly used material for packaging bags of various granules, electronic products, silicone, ear caps, and other materials.

[0004] Downstream customers of many thin film companies are paying increasing attention to the quality of the produced films, and many companies require that raw materials be sampled and tested upon arrival. Currently, the technology relies on manual sampling for quality inspection, which is prone to large testing errors and the accuracy of quality evaluation is affected by individual subjectivity. Summary of the Invention

[0005] To address the aforementioned shortcomings in the prior art, this invention provides a tensile testing system and method for cast CPE films that can evaluate the tensile quality and overall quality of cast CPE films from multiple perspectives.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for testing the tensile strength of cast CPE film is provided, comprising the following steps:

[0008] S1: Cut a cast CPE film of a specified length and width to use as the test material;

[0009] S2: Hang both ends of the cast CPE film on the thin film material testing machine. Install a surface light source larger than the area of ​​the cast CPE film on the back of the cast CPE film. Install a black screen on the front of the cast CPE film. The line connecting the center of the black screen and the center of the surface light source passes through the center of the cast CPE film. Obtain the image formed on the black screen after the light emitted by the surface light source passes through the cast CPE film, and use it as the first projected image.

[0010] S3: Drive the thin film material testing machine to stretch the cast CPE film with a set tension T. The displacement sensor collects the displacement W of the cast CPE film during stretching at a set time t.

[0011] S4: The displacement W of the nth time n The displacement W of the ntth time n-t By subtracting the values, we obtain the displacement change ΔW = W n -W n-t ;

[0012] S5: Compare the displacement change ΔW with the displacement change threshold. If ΔW ≤ displacement change threshold, it is determined that the cast CPE film has entered the plastic section from the elastic section. Record the displacement at this time as the tensile limit displacement W' of the cast CPE film and proceed to step S6; otherwise, continue to stretch the cast CPE film with tensile force T and return to step S3.

[0013] S6: Stop stretching the cast CPE film and keep it still. Take a picture of the image projected onto the black screen after the surface light source is refracted through the cast CPE film, and obtain the second projected image.

[0014] S7: Increase the tensile force and continue to stretch the cast CPE film until it breaks. Record the maximum tensile force applied by the film material testing machine before the film breaks, which is taken as the ultimate tensile force T' that the cast CPE film can withstand.

[0015] S8: Calculate the light transmittance change rate G and deformation area S of the stretched CPE film using the first and second projection images;

[0016] S9: Evaluate the grade Y of this batch of cast CPE film using the light transmittance change rate G, deformation area S, ultimate tensile force T', and ultimate tensile displacement W'.

[0017]

[0018] Among them, G X S X T' X W' X These are the allowable threshold values ​​for light transmittance change rate, deformation area, ultimate tensile force, and ultimate tensile displacement, respectively.

[0019] If Y = 0, then the batch of cast CPE film is deemed to be substandard and cannot be allowed to enter the market; it must be scrapped.

[0020] If Y = 1, then the quality of this batch of cast CPE film is determined to be low.

[0021] If Y = 2, then the quality of this batch of cast CPE film is determined to be medium grade;

[0022] If Y = 3, then the quality of this batch of cast CPE film is determined to be high-grade;

[0023] If Y = 4, then the quality of this batch of cast CPE film is determined to be of premium grade.

[0024] Further, step S8 includes:

[0025] S81: Convert the first projected image and the second projected image to grayscale to obtain a first grayscale image and a second grayscale image;

[0026] S82: Extract the gray value of each pixel in the first grayscale image and the second grayscale image, and calculate the average gray value P of all pixels in the first grayscale image;

[0027] S83: Compare the gray value H of each pixel in the second grayscale image with the average value P. If the gray value H ≥ the average value P, then the pixel is determined to be normally transparent; otherwise, the pixel is determined to be occluded.

[0028] S84: Calculate the light transmittance change rate G: Z / A using the total number of occluded pixels Z in the second projected image, where A is the total number of pixels in the second projected image;

[0029] S85: Compare the gray value H of each pixel in the second projected image with the boundary gray value threshold H1. If the gray value H is equal to the boundary gray value threshold H1, it proves that the pixel is the boundary point of the CPE film projected onto the black screen.

[0030] S86: Mark the boundary points on the second projected image. Establish a two-dimensional coordinate system on the second projected image and mark the coordinates (x, y, y) of each boundary point in the two-dimensional coordinate system. n y n );

[0031] S87: Calculate the area enclosed by the boundary points using the coordinates of each boundary point.

[0032] B=1 / 2[(x1×y2-x2×y1)+(x2×y3-x3×y2)+···(x n-1 ×y n -x n ×y n-1 )];

[0033] S88: Calculate the initial area B1 using the length and width of the cast CPE film in step S1, and calculate the deformed area S: S = B1 - B.

[0034] A testing system is provided for the tensile testing method of the above-mentioned cast CPE film, comprising:

[0035] Thin film material testing machine: used to perform tensile tests on cast CPE films to be tested;

[0036] Surface light source: Provides a uniform light source for testing the transmittance change rate of cast CPE film;

[0037] Camera: Captures the image formed by a surface light source being refracted through the cast CPE film onto a black screen;

[0038] Data processing system: The tensile force and displacement W collected by the thin film material testing machine, and the images captured by the camera are sent to the data processing system. The data processing system processes the data, evaluates the grade of the tested cast CPE film, and displays it on the display screen.

[0039] The beneficial effects of this invention are as follows: This invention conducts tensile tests on cast CPE films, comprehensively analyzes the performance of cast CPE films after stretching, and further evaluates the grade of cast CPE films. It avoids the influence of subjective human factors, can objectively and accurately evaluate the performance of films after stretching, and directly obtains the grade evaluation structure. This effectively improves the efficiency of quality inspection of produced cast CPE films, has a high degree of automation, and produces accurate evaluation results. Furthermore, it can comprehensively consider the impact of stretching on the quality of cast CPE films from multiple aspects such as light transmittance change rate, deformation area, ultimate tensile force, and tensile ultimate displacement, resulting in highly reliable evaluation results. Attached Figure Description

[0040] Figure 1 This is a flowchart of the tensile testing method for cast CPE film. Detailed Implementation

[0041] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0042] The tensile testing method for cast CPE film in this scheme includes the following steps:

[0043] S1: Cut a cast CPE film of a specified length and width to use as the test material;

[0044] S2: Hang both ends of the cast CPE film on the thin film material testing machine. Install a surface light source larger than the area of ​​the cast CPE film on the back of the cast CPE film. Install a black screen on the front of the cast CPE film. The line connecting the center of the black screen and the center of the surface light source passes through the center of the cast CPE film. Obtain the image formed on the black screen after the light emitted by the surface light source passes through the cast CPE film, and use it as the first projected image.

[0045] S3: Drive the thin film material testing machine to stretch the cast CPE film with a set tension T. The displacement sensor collects the displacement W of the cast CPE film during stretching at a set time t.

[0046] S4: The displacement W of the nth time n The displacement W of the ntth time n-t By subtracting the values, we obtain the displacement change ΔW = W n -W n-t ;

[0047] S5: Compare the displacement change ΔW with the displacement change threshold. If ΔW ≤ displacement change threshold, it is determined that the cast CPE film has entered the plastic section from the elastic section. Record the displacement at this time as the tensile limit displacement W' of the cast CPE film and proceed to step S6; otherwise, continue to stretch the cast CPE film with tensile force T and return to step S3.

[0048] S6: Stop stretching the cast CPE film and keep it still. Take a picture of the image projected onto the black screen after the surface light source is refracted through the cast CPE film, and obtain the second projected image.

[0049] S7: Increase the tensile force and continue to stretch the cast CPE film until it breaks. Record the maximum tensile force applied by the film material testing machine before the film breaks, which is taken as the ultimate tensile force T' that the cast CPE film can withstand.

[0050] S8: Calculate the light transmittance change rate G and deformation area S of the stretched CPE film using the first and second projection images; Step S8 includes:

[0051] S81: Convert the first projected image and the second projected image to grayscale to obtain a first grayscale image and a second grayscale image;

[0052] S82: Extract the gray value of each pixel in the first grayscale image and the second grayscale image, and calculate the average gray value P of all pixels in the first grayscale image;

[0053] S83: Compare the gray value H of each pixel in the second grayscale image with the average value P. If the gray value H ≥ the average value P, then the pixel is determined to be normally transparent; otherwise, the pixel is determined to be occluded.

[0054] S84: Calculate the light transmittance change rate G: Z / A using the total number of occluded pixels Z in the second projected image, where A is the total number of pixels in the second projected image;

[0055] S85: Compare the gray value H of each pixel in the second projected image with the boundary gray value threshold H1. If the gray value H is equal to the boundary gray value threshold H1, it proves that the pixel is the boundary point of the CPE film projected onto the black screen.

[0056] S86: Mark the boundary points on the second projected image. Establish a two-dimensional coordinate system on the second projected image and mark the coordinates (x, y, y) of each boundary point in the two-dimensional coordinate system.n y n );

[0057] S87: Calculate the area enclosed by the boundary points using the coordinates of each boundary point.

[0058] B=1 / 2[(x1×y2-x2×y1)+(x2×y3-x3×y2)+···(x n-1 ×y n -x n ×y n-1 )];

[0059] S88: Calculate the initial area B1 using the length and width of the cast CPE film in step S1, and calculate the deformed area S: S = B1 - B.

[0060] S9: Evaluate the grade Y of this batch of cast CPE film using the light transmittance change rate G, deformation area S, ultimate tensile force T', and ultimate tensile displacement W'.

[0061]

[0062] Among them, G X S X T' X W' X These are the allowable thresholds for light transmittance change rate, deformation area, ultimate tensile force, and tensile limit displacement, respectively. An excessively large light transmittance change rate (G) indicates poor light transmittance of the stretched cast CPE film, making it unsuitable for transparent packaging. An excessively large deformation area (S) indicates significant shrinkage of the stretched cast CPE film, indicating poor quality. An excessively small ultimate tensile force (T') indicates weak tensile strength of the cast CPE film. The tensile limit displacement also indicates poor extensibility.

[0063] If Y = 0, then the batch of cast CPE film is deemed to be substandard and cannot be allowed to enter the market; it must be scrapped.

[0064] If Y = 1, then the quality of this batch of cast CPE film is determined to be low.

[0065] If Y = 2, then the quality of this batch of cast CPE film is determined to be medium grade;

[0066] If Y = 3, then the quality of this batch of cast CPE film is determined to be high-grade;

[0067] If Y = 4, then the quality of this batch of cast CPE film is determined to be of premium grade.

[0068] The testing system used in the above tensile testing method for cast CPE film includes:

[0069] Thin film material testing machine: used to perform tensile tests on cast CPE films to be tested;

[0070] Surface light source: Provides a uniform light source for testing the transmittance change rate of cast CPE film;

[0071] Camera: Captures the image formed by a surface light source being refracted through the cast CPE film onto a black screen;

[0072] Data processing system: The tensile force and displacement W collected by the thin film material testing machine, and the images captured by the camera are sent to the data processing system. The data processing system processes the data, evaluates the grade of the tested cast CPE film, and displays it on the display screen.

[0073] This invention conducts tensile tests on cast CPE films, comprehensively analyzes the performance of the cast CPE films after stretching, and further evaluates the grade of the cast CPE films. It avoids the influence of subjective human factors, can objectively and accurately evaluate the performance of the film after stretching, and directly obtains the grade evaluation structure. It effectively improves the efficiency of quality inspection of the produced cast CPE films, has a high degree of automation, and the evaluation results are accurate. Furthermore, it can comprehensively consider the impact of stretching on the quality of cast CPE films from multiple aspects such as light transmittance change rate, deformation area, ultimate tensile force, and ultimate tensile displacement, resulting in highly reliable evaluation results.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0075] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for testing the tensile strength of cast CPE film, characterized in that, Includes the following steps: S1: Cut a cast CPE film of a specified length and width to use as the test material; S2: Hang both ends of the cast CPE film on the thin film material testing machine. Install a surface light source larger than the area of ​​the cast CPE film on the back of the cast CPE film. Install a black screen on the front of the cast CPE film. The line connecting the center of the black screen and the center of the surface light source passes through the center of the cast CPE film. Obtain the image formed on the black screen after the light emitted by the surface light source passes through the cast CPE film, and use it as the first projected image. S3: Drive the thin film material testing machine to stretch the cast CPE film with a set tension T. The displacement sensor collects the displacement W of the cast CPE film during stretching at a set time t. S4: The displacement W of the nth time n The displacement W of the ntth time n-t By subtracting the values, we obtain the displacement change ΔW = W n -W n-t ; S5: Compare the displacement change ΔW with the displacement change threshold. If ΔW ≤ displacement change threshold, it is determined that the cast CPE film has entered the plastic section from the elastic section. Record the displacement at this time as the tensile limit displacement W' of the cast CPE film and proceed to step S6; otherwise, continue to stretch the cast CPE film with tensile force T and return to step S3. S6: Stop stretching the cast CPE film and keep it still. Take a picture of the image projected onto the black screen after the surface light source is refracted through the cast CPE film, and obtain the second projected image. S7: Increase the tensile force and continue to stretch the cast CPE film until it breaks. Record the maximum tensile force applied by the film material testing machine before the film breaks, which is taken as the ultimate tensile force T' that the cast CPE film can withstand. S8: Calculate the light transmittance change rate G and deformation area S of the stretched CPE film using the first and second projection images; S9: Evaluate the grade Y of this batch of cast CPE film using the light transmittance change rate G, deformation area S, ultimate tensile force T', and ultimate tensile displacement W'. Among them, G X S X T' X W' X These are the allowable threshold values ​​for light transmittance change rate, deformation area, ultimate tensile force, and ultimate tensile displacement, respectively. If Y = 0, then the batch of cast CPE film is deemed to be substandard and cannot be allowed to enter the market; it must be scrapped. If Y = 1, then the quality of this batch of cast CPE film is determined to be low. If Y = 2, then the quality of this batch of cast CPE film is determined to be medium grade; If Y = 3, then the quality of this batch of cast CPE film is determined to be high-grade; If Y = 4, then the quality of this batch of cast CPE film is determined to be of premium grade. Step S8 includes: S81: Convert the first projected image and the second projected image to grayscale to obtain a first grayscale image and a second grayscale image; S82: Extract the gray value of each pixel in the first grayscale image and the second grayscale image, and calculate the average value P of the gray values ​​of all pixels in the first grayscale image; S83: Compare the gray value H of each pixel in the second grayscale image with the average value P. If the gray value H ≥ the average value P, then the pixel is determined to be normally transparent; otherwise, the pixel is determined to be occluded. S84: Calculate the light transmittance change rate G: Z / A using the total number of occluded pixels Z in the second projected image, where A is the total number of pixels in the second projected image; S85: Compare the gray value H of each pixel in the second projected image with the boundary gray value threshold H1. If the gray value H is equal to the boundary gray value threshold H1, it proves that the pixel is the boundary point of the CPE film projected onto the black screen. S86: Mark the boundary points on the second projected image. Establish a two-dimensional coordinate system on the second projected image and mark the coordinates (x, y, y) of each boundary point in the two-dimensional coordinate system. n y n ); S87: Calculate the area enclosed by the boundary points using the coordinates of each boundary point. B=1 / 2[(x1×y2-x2×y1)+(x2×y3-x3×y2)+···(x n-1 ×y n -x n ×y n-1 )]; S88: Calculate the initial area B1 using the length and width of the cast CPE film in step S1, and calculate the deformed area S: S = B1 - B.

2. A testing system used in the tensile testing method for the cast CPE film according to claim 1, characterized in that, include: Thin film material testing machine: used to perform tensile tests on cast CPE films to be tested; Surface light source: Provides a uniform light source for testing the transmittance change rate of cast CPE film; Camera: Captures the image formed by a surface light source being refracted through the cast CPE film onto a black screen; Data processing system: The tensile force and displacement W collected by the thin film material testing machine, and the images captured by the camera are sent to the data processing system. The data processing system processes the data, evaluates the grade of the tested cast CPE film, and displays it on the display screen.

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